Here’s a fabulous STEM activity for kids!  Build a working Trebuchet out of craft sticks.  You can construct and play with the trebuchet, or take it a step further by printing the recording sheets included in the post.  There are two experiments to perform with the trebuchet, and students can record their results.

This was the first time that we have tried building a trebuchet, and it was a lot of fun!  Like a catapult, a trebuchet was used to hurl large projectiles at an enemy.  When we think of a catapult, we usually think of a machine that uses tension to launch a projectile.  A trebuchet is a type of catapult, but it uses gravity to launch the projectile.  How does that work?  A trebuchet has a counterweight that is raised and then dropped.  When the weight falls, it pulls the launching arm up!

We used a rock as our counterweight.  Simply pull down the arm…

Then let go!  The weight of the rock causes the arm to drop down, and it launches the projectile!

Ready to build a trebuchet?

To make one, you will need:

  • Jumbo craft sticks
  • Rubber bands
  • String
  • Duct tape
  • Hot glue gun
  • A dowel rod
  • Plastic cap from a juice bottle or something similar

We chose craft sticks as our primary material because we have a ton of them, ha.  They are inexpensive and easy to find, making this a project that most teachers could do with a realistic budget.  If you have a different idea for building materials, I’m sure there are better options out there!

This project was primarily designed by my 13 year old, but younger kids could definitely build one, especially if they are using these pictures as a guide.

The main legs of the trebuchet are made out of 3 craft sticks, which are overlapping and glued together.

The launching arm is made of more overlapping craft sticks.  We used string to tie the arm to a dowel rod.  Then we glued a juice bottle lid to the arm to hold the projectile.

We wanted to keep the rock from falling off, so we wrapped a rubber band around it.  Then we ran some string under the rubber band and then tied it to the launching arm.  We secured the string to the launching arm with duct tape to keep it secure.

Aidan and I tested out the trebuchet, and could tell that it worked, so then we worked on making the launching arm more stable.

In order to get enough torque to launch the projectile, we needed to use a lot of weight.  Aidan added pieces of craft sticks on both sides to hold the dowel rod in place.  Otherwise it would sometimes jump out of its track during the launch.

Make it an Experiment!

Will the trebuchet shoot farther with a long projectile arm or a short one?  To test this, we adapted our trebuchet by adding more craft sticks to make the arm longer.  Then we added juice caps in two places as shown below.

(The projectile traveled farther when launched from the end of the arm, but let your kids figure this out themselves!)

We also tested our trebuchet to see what types of objects would travel the farthest.  We tried a ping pong ball, a little wooden ball (from the craft store), a bouncy ball, a larger bouncy ball, a pom pom ball, and a little stone.

It works best to have one person to launch the trebuchet, while another person marks the place where the object lands.  It’s hard to see exactly where it lands from the perspective of the launcher.  Measure each trial and record your results!

Kids can easily record their results on the recording sheet – download it below.

The recording sheet has two pages – one for each experiment.

Print a Recording Sheet

I created two versions – one for 3rd grade and under and one for 4th grade and up.  The older kids version includes a column for recording the average distance that each projectile traveled.  It also includes a space for students to record possible sources of error in the experiment.  They’re both free, so feel free to download both and see which would work better with your kids or students!

Click your choice below:

Trebuchet Recording Sheet

Trebuchet Recording Sheet – Grades 4 and up

Have fun tinkering!

3 Comments

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  1. Heidi Pittman Aug 5, 2017

    This is actually a counterweight catapult. Trebuchets have a sling hanging from the launch side that holds the projectile.

    Reply
    1. memeys Sep 28, 2018

      are you gay

      Reply
    2. A puzzled parent Nov 21, 2018

      So... how do you build it?

      Reply
      1. A puzzled parent Nov 21, 2018

        Never mind! Found it!

        Reply
      2. Trebuchet Tom Feb 13, 2019

        Can it launch a 90kg projectile over 300m?

        Reply

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